1. Field of the Invention
The present invention relates to a method for calculating parameters in a road design of a S type, a complex type and an egg type clothoid, and in particular to a method for calculating a parameter value capable of determining the size of a clothoid that is inserted when designing a S-shaped and interchange, a connection road, etc. in an egg shape.
2. Description of the Background Art
Generally, when a vehicle parks at a road directly connecting a straight line and a circle, the vehicle receives a sharp centrifugal acceleration or a rotational angular speed when the radius of a circle is small, so that passenger feels uncomfortable or there is something dangerous in driving. Therefore, a smooth curve may be inserted between the connections for thereby decreasing the above problems. The used in the present invention are defined as follows.
“Clothoid” represents a curve of which a curvature (reverse number of radius) is increased in proportion to the length of a curve and a driving trace that a vehicle makes when the vehicle runs at a constant speed, and the rotation angular speed of the front wheels is constant.
The following equations are obtained at all points on one clothoid.
(curvature radius R at a certain point)×(curve length L from the center of the clothoid to the point)=(constant value A2). The above equation (namely, R×L=A2 is called the basic formula of the clothoid. All elements of the clothoid are induced based on the above basic formula.
Here, the clothoid may be classified into a basic type (a connection in a sequence of straight line, clothoid, circular curve, clothoid, and straight line), a S shape (two clothoid are inserted between reflection curves), an egg type (clothoid is inserted between double center curves), a protrusion type (two clothoid bent in the same direction are connected with each other), and a complex type (at least two clothoid bent in the same direction). The basic type has been basically used during the design. The basic type design can be easily achieved using the clothoid formulas). The complex type has not used yet. The interchange and connection road are designed in the egg type. The calculation methods of the S type, complex type and egg type are difficult. It is impossible to easily calculate with only the basis formula.
In the S type and egg type, the important thing is to calculate the value of the parameter A determining the size of the clothoid inserted. It is impossible to easily calculate with only the basic formula of the clothoid differently from the basic type.
The egg type has been generally used for the interchange or the connection road. The interchanges are actually used in a combination of one or at least two egg types. The egg type has been generally used in the interchanges of a straight connection type, clover type and trumpet type. Each type can be combined in the independent egg type. The forward direction egg type is an egg type that the linearity is formed in the directions of the entrance and exist axis crossing points. FIG. 1 is a view illustrating the type of a forward direction egg type.
The backward direction egg type is a type that the linearity is formed in the direction of the entrance and exist axis crossing points. FIG. 2 is a view of the backward direction egg type.
The S shape egg type is an egg type that a smoothing curve is installed between the short curves bent in the opposite direction. FIG. 3 is a view of the egg type.
The S type clothoid is the type that the clothoid curve is installed so that the viewing times are same with respect to two circles positioned in the direction opposite to the common axis. Here, the parameter represents the value A of the parameter of the clothoid curve.
The double egg type is the type that the connection is made using two egg types based on the assistant circle in the case that two circles are crossed or are distanced. The double egg type can be classified into four types as shown in FIG. 4. Namely, there are (i) the type that uses the assistant circle including two crossing circles, (ii) the type that uses the assistant circle having two distanced circles, (iii) the type that uses the assistant circle included in two crossing circles and (iv) the type that uses the assistant circle used because the distance in the radiuses of two circles is too large.
The conventional design method of the S type and egg type roads will be described.
[Conventional Design Method of S Shape Clothoid]
When the S shape clothoid curve is designed, the smoothing curve is installed with respect to the common axis so that a straight line does not exist between the smoothing curves of two circles. The parameter values A with respect to the circles 1 and 2 are generally set with the same values, but may be different in some special cases based on the design characteristic. However, there is not any formula for accurately calculating the parameters with respect to the S type clothoid. Therefore, the S type clothoid can be not designed at one time, so that it is separately designed by classifying the circles 1 and 2. Namely, the circle 1 is designed with a symmetric type or a non-symmetric type. The design specification with respect to the circle 2 is designed so that a straight line is not formed between the circles 1 and 2 using a result of the design of the circle 1. However, in the conventional method, it is impossible to set the accurate specification, and it takes long time. Many tests should be performed until a desired result is obtained.
[Conventional Method of Egg Type Design]
The important thing of the egg type design is to determine the parameter A with respect to the smoothing curve installed between a larger circle and a smaller circle. However, there is not currently any formula for accurately calculating the parameter value A. In addition, it is impossible to accurately design and calculate each program. In the currently available programs, the design is performed at one time in the case that a designer designates the parameter value A like the radius of the circle. However, it is actually impossible to calculate the parameter value A for a desired design. Therefore, a proper value is designated and designed. The above process is repeated until a desired design is achieved.
Generally, the value A is not integer and should be calculated down to four˜six decimal places in order to use an accurate value in a permissible value in the actual work. Therefore, much efforts should be provided in order to determine the value within a permissible error in the actual work. Since the egg type is mainly used in the interchange or the connection road, the coordinates of the entrance and exist axis at which the egg type is installed has been already determined. Therefore, the start point of the egg type should be provided at the axis of the entrance as a result of the egg type design when designing the egg type, and the ending point should be provided on the axis of the exist, so that the linearities of the front and rear sides of the egg type are not changed. The egg type is not designed at a desired position unless the parameter value A of the egg type is designated with an accurate value within the permissible error. The linearity portions after the egg type get changed as compared to the set linearity.
The egg type generally uses a single egg type. In a special case based on the design characteristic, the double egg type may be used. In the double egg type, there is not any accurate design method.
As the prior art related to the present invention, there is an applied measurement (written by Hong Hyun Ki and published by Seoul Industrial University and published n Feb. 26, 1993) in which the basic formulas and assistant materials for design with respect to the S shape clothoid, egg type clothoid and complex type clothoid design calculations are disclosed. The above theories are obtained based on the books of DIE KLOTOIDE als TRANSSIERUNGSELEMENT published in 1964 in Germany and STRASENPLANUNG mit KLOTOIDEN written by Horst Osterloh and published in 1965.
The value A in the egg type can be obtained using the diagram of Horst Osterloh and the table made by Kasper, Schuerba and Lorenz. The diagram of Osterlok can not be actually used in the actual work, and the table made by Kasper, Schuerba, Lorenz can be actually used in the actual work and can be applied in the programs. In this case, the table is used, so that the size of the program is increased, and the values of the tables are informal values, and multiple tables should be used. The values are obtained by approximate values. In the case that the values are out of a certain range, there may be a big difference from the actual value.